U.S. patent application number 09/961393 was filed with the patent office on 2002-05-30 for aliphatic polyester compositions, films made thereof and laminates thereof.
Invention is credited to Itoh, Suekazu, Narita, Junichi, Sawai, Tohru, Takeishi, Ichiro.
Application Number | 20020065345 09/961393 |
Document ID | / |
Family ID | 26600948 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020065345 |
Kind Code |
A1 |
Narita, Junichi ; et
al. |
May 30, 2002 |
Aliphatic polyester compositions, films made thereof and laminates
thereof
Abstract
Disclosed is a composition provided with biodegradable property
and transparency which is excellent in heat sealing property at low
temperatures, peelability and adhesiveness to substrate as well as
a film or laminate of the composition. The composition comprises as
indispensable components thereof polylactic acid, an aliphatic
polyester and a tackifier.
Inventors: |
Narita, Junichi;
(Ibaraki-ken, JP) ; Sawai, Tohru; (Ibaraki-Ken,
JP) ; Takeishi, Ichiro; (Ibaraki-ken, JP) ;
Itoh, Suekazu; (Ibaraki-ken, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW.
SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
26600948 |
Appl. No.: |
09/961393 |
Filed: |
September 25, 2001 |
Current U.S.
Class: |
524/271 ;
428/480; 428/481 |
Current CPC
Class: |
Y10T 428/2878 20150115;
C08J 5/18 20130101; B32B 27/10 20130101; C08L 67/04 20130101; Y10T
428/2817 20150115; Y10T 428/3179 20150401; Y10T 428/2826 20150115;
Y10T 428/31786 20150401; C08L 67/04 20130101; Y10T 428/2813
20150115; C08J 2367/04 20130101; C08L 67/04 20130101; C08L 2666/02
20130101; B32B 27/36 20130101; C08L 67/04 20130101 |
Class at
Publication: |
524/271 ;
428/481; 428/480 |
International
Class: |
C08L 001/00; B32B
027/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2000 |
JP |
2000-296429 |
Aug 30, 2001 |
JP |
2001-262187 |
Claims
What is claimed is:
1. An aliphatic polyester composition possessing excellent heat
sealable property, which comprises 9-90% by weight of polylactic
acid (A), 90-9% by weight of an aliphatic polyester (B), and 1-20%
by weight of a tackifier (C).
2. An aliphatic polyester composition according to claim 1, wherein
the aliphatic polyester composition comprises 27-70% by weight of
polylactic acid (A), 70-27% by weight of an aliphatic polyester (B)
and 3-10% by weight of a tackifier (C).
3. An aliphatic polyester composition according to claim 1, wherein
the aliphatic polyester (B) is an aliphatic polyester obtained by
ring-opening polymerization of a cyclic lactone.
4. An aliphatic polyester composition according to claim 1, wherein
the tackifier (C) is selected from a rosin derivative and an
aliphatic cyclic hydrocarbon resin.
5. A biodegradable film made of the aliphatic polyester composition
by way of any suitable molding method.
6. A laminate which comprised of a substrate and an aliphatic
polyester composition on at least one surface of the substrate, the
aliphatic polyester composition possessing excellent heat sealable
property and comprising 9-90% by weight of polylactic acid (A),
90-9% by weight of an aliphatic polyester (B) and 1-20% by weight
of a tackifier (C).
7. A laminate according to claim 6, wherein the substrate is a
biodegradable polymer.
8. A laminate according to claim 6, wherein the substrate is paper.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an aliphatic polyester
composition suitable for obtaining films provided with
biodegradable property which are excellent in transparency,
interlaminar adhesiveness and heat sealing strength as well as
films and laminates made thereof.
[0003] 2. Description of the Prior Art
[0004] Polylactic acid and an aliphatic polyester, which are
representative examples of a biodegradable polymer, are higher in
crystallinity and rigid in molecular structure so that they are
greater in heat of fusion on heat sealing and thus poor in
heat-sealing property. All of the biodegradable polymers have a
melting point of at most about 200.degree. C. Thus, a difference in
melting point is not distinct among the materials in a multi-layer
film of a substrate/binder/sealant.
[0005] As heating of the film is effected from the side of the
substrate, transmission of heat toward the sealant is insufficient
if the heat sealing temperature is low, so that heat sealing
strength of the resultant laminated film becomes poor. On the other
hand, if the heat sealing temperature is elevated to enable
transmission of heat to the sealant sufficiently, the substrate may
also be molten so that thickness of the whole laminated film
becomes thin to cause a phenomenon called "edge breaking" which
means breaking of the film from the side of edge. Accordingly, it
is impossible to manufacture a film container (bag) for packing
liquid from such film. Even if a bag is manufactured, it utterly
fails to satisfy the demand for packing liquid. As a means for
overcoming such problems, a method wherein polylactic acid is mixed
with an aliphatic polyester in a composition to improve heat
sealing property (Japanese Laid-open Patent Applns. Nos. Hei.
9-157408 and Hei. 11-222528) or a biodegradable packaging material
wherein such composition is utilized as a heat sealing layer
(Japanese Laid-open Patent Appln. Hei. 11-20084) are proposed
hitherto.
PROBLEMS TO BE SOLVED BY THE INVENTION
[0006] Such methods are effective for improving heat sealing
property but are still insufficient in the effect and involves in
some cases damaging transparency that is a character of the
biodegradable polymer. In addition, such compositions are
insufficient in a good balance of heat sealing strength and
peelability when used as a cover or lid material for plastic
containers comprised of polylactic acid.
[0007] In case two multilayer films made of a stretched polylactic
acid film laminated with a heat sealing layer of a composition of
the polylactic acid and an aliphatic polyester is heat-sealed
mutually, for example, the heat sealing strength may significantly
be enhanced. However, when the aforesaid composition layer is heat
sealed with a polylactic acid film, the heat sealing strength is
still low so that the effect of improving in heat sealability at
low temperature is insufficient. Thus, its packaging application is
inevitably limited as compared with the conventional polyolefin
packaging materials. In addition, there may be the case wherein a
covering material excellent in peelability is not obtained by using
a heat sealing layer of the aforesaid composition layer on a
container obtained, for example, by thermally molding polylactic
acid sheet.
[0008] Under the above circumstances, there is a great demand in
this art to develop a new type biodegradable aliphatic polyester
composition which overcomes the problems seen in the prior art
compositions and can be furnished with excellent heat sealable
property at low temperatures and peelability in addition to the
inherent biodegradable property and transparency.
BRIEF SUMMARY OF THE INVENTION
[0009] 1. Objects of the Invention:
[0010] It is an object of the present invention to improve heat
sealing property at low temperatures without spoiling biodegradable
property which is an inherent character of biodegradable polymers
as well as transparency.
[0011] It is another object of the present invention to provide an
aliphatic polyester composition possessing excellent heat sealing
strength and peelability as well as the inherent biodegradable
property and transparency.
[0012] It is still another object of the present invention to
provide a film made of the aliphatic polyester composition by way
of any suitable molding method.
[0013] It is still further object of the present invention to
provide a laminate possessing sufficient heat sealing strength and
peelability as a thermally fusible layer of a biodegradable polymer
as well as excellent adhesiveness to a substrate.
[0014] Other and further objects, features and advantages of the
present invention will become apparent more fully from the
following description.
[0015] 2. Means of solving the Problems:
[0016] Taking the aforementioned circumstances into consideration,
the present inventors have made extensive research for developing a
new type aliphatic polyester composition which overcomes the
various drawbacks seen in the prior art biodegradable polymer
compositions and enables the production of a biodegradable
composition enhanced in heat seal strength and peelability without
spoiling the inherent biodegradable property and transparency. As a
result of such extensive research, it has now been found
surprisingly that an aliphatic polyester composition composed of a
specific proportion of polylactic acid, an aliphatic polyester and
a tackifier exhibits a remarkably high heat sealing strength and
peelability while maintaining good adhesion to a substrate. The
present invention has been accomplished on the basis of the above
finding.
[0017] In accordance with an embodiment of the present invention,
there is provided an aliphatic polyester composition possessing
excellent heat sealable property, which comprises 9-90% by weight
of polylactic acid (A), 90-9% by weight of an aliphatic polyester
(B), and 1-20% by weight of a tackifier (C).
[0018] In accordance with another embodiment of the present
invention, there is provided a film made of the aforesaid aliphatic
polyester composition by way of any suitable molding method.
[0019] In accordance with still another embodiment of the present
invention, there is provided a laminate which comprised of a
substrate and an aliphatic polyester composition on at least one
surface of the substrate, the aliphatic polyester composition
possessing excellent heat sealable property and comprising 9-90% by
weight of polylactic acid (A), 90-9% by weight of an aliphatic
polyester (B) and 1-20% by weight of a tackifier (C).
[0020] In a preferred embodiment of the present invention, the
aliphatic polyester (B) is an ester obtained by ring-opening
polymerization of a cyclic lactone and the tackifier (C) is a rosin
derivative or an aliphatic cyclic hydrocarbon resin.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Below is a detailed description on the individual components
constituting the aliphatic polyester composition of the present
invention.
[0022] Polylactic acid (A):
[0023] Polylactic acid (A) used in the aliphatic polyester
composition generally stands for homopolymers of lactic acid,
including poly(L-lactic acid) in which the structure unit is
L-lactic acid, poly(D-lactic acid) in which the structure unit is
D-lactic acid and poly(DL-lactic acid) in which the structure unit
is DL-lactic acid, 1.e. a racemic equiamount mixture of D-lactic
acid and L-lactic acid; copolymers of lactic acid containing lactic
acid as the predominant component and a small proportion of a
copolymerizable comonomer, for example, a copolymer of lactic acid
with less than 50% by weight, preferably not more than 30% by
weight, more preferably not more than 10% by weight of glycolic
acid; and a mixture of these. Illustrative of the comonomer
copolymerizable with lactic acid are, for example, a
3-hydroxybutyrate, caprolactone, glycolic acid and the like. Among
these polymers, a homopolymer of lactic acid can preferably be used
as it excels in transparency.
[0024] Any of the known polymerization methods, such as
polycondensation method and ring-opening polymerization can be
adopted for polymerization of lactic acid. In polycondensation
method, for example, L-lactic acid, D-lactic acid or a mixture of
these is directly subjected to dehydropolycondensation whereby a
polylactic acid of a desired composition can be obtained.
[0025] In the ring-opening polymerization method, a lactide which
is a cyclic dimer of lactic acid is subjected to polymerization by
the aid of a polymerization-adjusting agent and a catalyst thereby
obtaining polylactic acid. A lactide includes L-lactide which is a
dimer of L-lactic acid, D-lactide which is a dimer of D-lactic acid
and DL-lactide which is a condensate of L-lactic acid and D-lactic
acid. These isomers can be mixed and polymerized, if necessary, to
obtain polylactic acid having any desired composition and
crystallinity.
[0026] A small amount of a chain-extending agent, for example, a
diisocyanate compound, an epoxy compound or an acid anhydride can
be used for the purpose of increasing molecular weight of the
polylactic acid. A weight average molecular weight of the
polylactic acid is usually within the range of 60,000-1,000,000. If
the molecular weight is less than 60,000, a practical physical
property may hardly be exhibited according to the intended use. On
the other hand, if the molecular weight is more than 1,000,000, the
melt viscosity may be excessively high to make molding workability
poor.
[0027] Aliphatic polyester (B):
[0028] Aliphatic polyester (B) used in the aliphatic polyester
composition includes, with the exception of the aforesaid
polylactic acid (A), an aliphatic polyester obtained by condensing
an aliphatic diol with an aliphatic dicarboxylic acid, an aliphatic
polyester obtained by ring-opening polymerization of a cyclic
lactone, a synthetic aliphatic polyester, an aliphatic polyester
biosynthesized in microorganism, etc.
[0029] Examples of the aliphatic polyester obtained by condensing
an aliphatic diol with an aliphatic dicarboxylic acid include those
obtained from ethylene glycol, 1,4-butanediol and
4-cyclohexanedimethanol, etc. as the aliphatic diol and succinic
acid, adipic acid, suberic acid, sebacic acid and
dodecanedicarboxylic acid, etc. as the aliphatic dicarboxylic acid.
Among these, at least one diol and at least one dicarboxylic acid
are selected and polycondensed and, if necessary, a chain-extending
agent such as an isocyanate compound may be sued to increase the
molecular weight of the polyester whereby a polymer having a
desired molecular weight can be obtained.
[0030] Examples of the aliphatic polyester obtained by ring-opening
polymerization of a cyclic lactone include polymers obtained by
polymerization of one or more cyclic monomers such as
.epsilon.-caprolactone, .delta.-valerolactone,
.beta.-methyl-.delta.-vale- rolactone, etc.
[0031] As the synthetic aliphatic polyester, there can be mentioned
copolymers of a cyclic acid anhydride and an oxlane compound, such
as a copolymer of succinic anhydride and ethylene oxide or
propylene oxide.
[0032] As the aliphatic polyester biosynthesized by microorganisms
is known an aliphatic polyester biosynthesized by acetyl coenzyme A
(Acetyl CoA) in micro-organisms including Alcaligenes eutorophus.
This aliphatic polyester is chiefly poly-.beta.-hydroxybutyric acid
(poly3HB). It is indusrially advantageous, however, to copolymerize
this with a valeric acid unit (HV) to form poly(3HB-co-3HV). An HV
copolymerizing ratio is generally 0-40%. It is also possible to
copolymerize this with a longer chain hydroxyalkanoate. Among the
aliphatic polyester (B), that obtained by ring-opening
polymerization of a cyclic lactone, in particular
poly(.epsilon.-caprolactone) is preferable as this polymer excels
in improving effect of enhancing heat sealing property at low
temperatures, heat sealing strength and softening.
[0033] Tackifier (C):
[0034] Illustrative of the tackifier (C) used in the aliphatic
polyester composition are, for example, a phenol type resin such as
coumarone-indene resin, p- tert-butylphenol-acetylene resin,
phenol-formaldehyde resin, terpene-phenol resin, and
xylene-formaldehyde resin; a terpene type resin such as
.beta.-pinen resin, .alpha.-pinene resin, dipenten base resin,
styrene-modified terpene resin, and synthetic polyterpene resin; a
terpene resin devoid of any polar group; a petroleum hydrocarbon
resin such as an aromatic hydrocarbon resin, an aliphatic
hydrocarbon resin, an aliphatic cyclic hydrocarbon resin, an
aliphatic and alicyclic petroleum resin, an aliphatic and aromatic
petroleum resin, and a hydrogenated hydrocarbon resin; and a rosin
derivative such as pentaerythritol ester of rosin, glycerol ester
of rosin, methyl ester of hydrogenated rosin, triethylene glycol
ester of hydrogenated rosin, a metal salt of a rosin ester, and a
special rosin ester having an acid number of 10 or less. Among
these, the aliphatic cyclic hydrocarbon resin, the metal salt of a
rosin ester, the special rosin ester having an acid number of 10 or
less are preferable since these excel; in improving effect of
transparency, heat sealing property at low temperatures, heat seal
strength. Further, a hydrogenated, particularly hydrogenated at
least 80%, especially at least 95% petroleum hydrocarbon resin
devoid of any polar group is preferable as it is very small in odor
and excellent in color tone.
[0035] Aliphatic polyester composition:
[0036] The aliphatic polyester composition of the present invention
is composed of the aforesaid polylactic acid (A), the aliphatic
polyester (B) and the tackifier (C) in a proportion of
(A):(B):(C)=9-90:90-9:1-20, preferably
(A):(B):(C)=27-70:70-27:3-10. By defining the proportion within the
above range, the composition in the form of a film is excellent in
transparency, bonding strength to a substrate, and flexibility. The
composition is also excellent in heat sealing property at low
temperatures and heat sealing strength when used as a heat sealable
layer on laminates.
[0037] The aforementioned proportion is critical for achieving the
desired properties. If the proportion of the polylactic acid (A) is
less than 9% by weight, transparency and rigidity of the resultant
film will be insufficient. On the other hand, the proportion
exceeds 90% by weight, impact strength and flexibility of the
resultant film may become inferior. If the proportion of the
aliphatic polyester (B) is less than 9% by weight, flexibility and
impact strength will be insufficient, and on the other hand, if the
proportion exceeds 90% by weight, transparency and rigidity may be
damaged. If the proportion of the tackifier (C) is less than 1% by
weight, the improving effect for heat sealing property at low
temperatures and heat sealing strength may not be exhibited. On the
other hand, if the proportion exceeds 20% by weight, transparency
may become poor or adhesiveness of the resulting film may become
excessive or viscosity at the time of melting will be reduced so
that molding property may seriously damaged or the improving effect
for heat sealing property may not be exhibited.
[0038] The aliphatic polyester composition of the present invention
is obtained by blending the individual ingredients (A), (B) and (C)
in the aforesaid proportion homogeneously by the aid of Henshell
mixer, V-blender, a ribbon blender or a tumbler mixer, or after
blending, further melt kneading the mixture by the aid of an
uniaxial extruder, a polyaxial extruder, Bambury mixer or the
like.
[0039] The aliphatic polyester composition of the present invention
is thermoplastic and may be incorporated, if necessary, with one or
more of ordinary additives such as antioxidants,
weathering-resistant stabilizers, antistatic agents, anti-clouding
agents and the like in an amount not damaging the object of the
present invention, separately at the time of incorporating the
ingredients (A), (B) and (C) or at the time of incorporating the
composition. The composition of the present invention may be in the
form of a mixture thus blended, a filmy structure or a sheet..
[0040] Films:
[0041] The composition of the present invention in the form of a
film or sheet can be manufactured by molding according to a variety
of known methods. For example, the indispensable ingredients (A),
(B) and (C) are blended in a given proportion and then treated
directly in a film-forming apparatus by the aid of a T-die or a
cyclic die to form a film. Alternatively, the ingredients (A), (B)
and (C) in a given proportion are blended previously and the
mixture is subjected to melt kneading in an extruder to form an
aliphatic polyester composition which is then molded to a film by
extruding by the aid of a T-die or cyclic die or subjected to press
molding. The film thus obtained may be used as such (single layer).
In case a laminate film is manufactured, however, the aliphatic
polyester composition as a heat sealable layer and a substrate are
coextruded by the aid of a multilayer die thereby to form a
laminated film. The aliphatic polyester composition may be extruded
onto a previously obtained substrate to form a laminate film, or
alternatively, films separately obtained may be bonded together to
form a laminate film. In case the film is used as a covering
material, a single layer film or a sheet or a laminate film each
provided with a heat sealable layer obtained according to the
aforementioned method may be used as such as a covering material or
may be printed. It is also possible to laminate a paper or foil
such as aluminum foil which has been printed or not yet by heat
with the film or sheet for a covering material. Depending on the
intended use, the film or sheet may previously be cut in conformity
with the size of a container for covering use.
[0042] Substrate:
[0043] Various materials usually employed as packaging material,
for example, a film, or sheet, cup, tray, or these foamy materials,
glass, metal, aluminum foil, or paper made of a polyolefin such as
polyethylene, polypropylene, polybutene, or polymethylpentene; a
polyester such as polyethylene terephthalate or polycarbonate; a
widely used polymer such as nylon, polystyrene, polyvinyl chloride,
polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol
copolymer, polymethylmeacrylate or ethylene-vinyl acetate
copolymer; a biodegradable polymer, such as polylactic acid or an
aliphatic polyester; a thermoplastic resin such as thermoplastic
polyurethane; a thermocurable resin such as a thermocurable
polyurethane, a phenol resin, a urea resin, a melamine rein, a
unsaturated polyester resin, an epoxy resin, a diallylphthalate
resin, a silicone resin or a polyimide resin are mentioned as a
substrate to be laminated with the aliphatic polyester composition
of the present invention. A film of such thermoplastic or
thermocurable resin may be non-stretched or uniaxially or biaxially
stretched It is a matter of course that the substrate may be
unilayer or bilayer or more.
[0044] Laminates:
[0045] A laminate of the present invention consists of a layer of
the aliphatic polyester composition and a layer of the
aforementioned substrate. Such laminate can be manufactured
according to various known methods; for example, the aliphatic
polyester composition and the substrate are coextruded by the aid
of a multilayer die to form a laminate film. Otherwise, the
aliphatic polyester composition is extruded on the previously
obtained substrate to form a laminate film or sheet. Furthermore,
both is separately extruded and both films are bonded together to
form a laminate. It is a matter of course that a laminate of the
biodegradable polymer and paper or the like is biodegradable per
se. It is also needless to say that the laminate of the present
invention may be thermally deformed, irrespective of whether its
form is a film or sheet, to form a various kinds of shape according
to the intended uses, e.g. a tray, a cup or a bottle.
EFFECT OF THE INVENTION
[0046] The aliphatic polyester composition of the present invention
is per se biodegradable and therefore preferable as a sealant film
or a material for a sealant layer in a laminate film or sheet. In
addition to the inherent nature of biodegradable, the composition
is excellent in transparency and good in balance of flexibility and
rigidity. A sealant film or a sealant layer of the composition of
this invention may be enhanced, if necessary, in heat sealing
property at low temperatures, heat sealing strength. In case a
laminate involving the composition of the invention is used as a
covering material for a container, the degree of peelable strength
may be varied, if necessary, according to the intended use.
[0047] The aliphatic polyester composition of the present invention
excels in heat sealability at low temperatures in comparison with
the conventional biodegradable heat sealing materials so that the
composition may be laminated with a substrate to form a packaging
material. As the aliphatic polyester composition pet se is of
biodegradable, it can be used for other biodegradable material as
substrate which is generally not higher in heat-resistance, the
resultant laminate per se will also furnished with biodegradable
property and good transparency so that the laminate will be
suitable as a packaging material excellent in balance of physical
properties such as rigidity and flexibility. In case the
composition is used as a covering material for a container
comprising a biodegradable material, it becomes a covering material
of good peelability. Furthermore, the aliphatic polyester
composition of the present invention can easily be laminated with
paper or easily peelable therefrom so that a container per se made
by combining the composition with paper is also biodegradable and
can be separated after use by peeling the composition from the
paper to be recovered as source. It is possible to vary the
proportion of the individual constituents of the aliphatic
polyester composition within the range defined in the present
invention so that sealing property at low temperatures and heat
sealing strength can be enhanced or freely be varied.
EXAMPLES
[0048] The present invention will now be illustrated in more detail
by way of Examples and Comparative Examples. It is however to be
construed that the present invention is not limited by these
Examples.
[0049] Materials used in Examples and Comparative Examples are
those listed as follows:
[0050] (1) Polylactic acid (A) (PLA):
[0051] produced by Mitsui Chemicals Inc. (Japan), a trade name
LACEA H-100, specific gravity: 1.26, Vicat softening point:
58.degree. C., MFR (190.degree. C., load: 2160 g) 13 g/10 min.
[0052] (2) Aliphatic polyester (B) (poly-.epsilon.-caprolactone:
PCL):
[0053] Produced by Daicel Chemical (Japan), a trade name CELGREEN
PH 7, specific gravity: 1.14, Vicat softening point: 55.degree. C.,
MFR (190.degree. C., load: 2160 g) 1.7 g/10 min.
[0054] (3) Aliphatic polyester (B') (polybutylene succinate
adipate: PBSA):
[0055] Produced by Showa Highmolecule (Japan), a trade name:
BIONOLLE 3020, specific gravity: 1.23, MFR (190.degree. C., load:
2160 g) 28 g/10 min.
[0056] (4) Tackifier (C) (Metal salt of specific rosin ester:
Tackifier-1):
[0057] Produced by Arakawa Chemical (Japan), a trade name KE-359,
Vicat softening point: 96-106.degree. C., an acid number: 8-18
[0058] (5) Tackifier (C') (A specific rosin ester:
Tackifier-2):
[0059] Produced by Arakawa Chemical (Japan), a trade name SUPER
ESTER A-100, Vicat softening point. 95-105.degree. C., an acid
number: not more than 10
[0060] (6) Tackifier (C") (An aliphatic cyclic hydrocarbon:
Tackifier-3):
[0061] Produced by Arakawa Chemical (Japan), a trade name ARKON
P-100, Vicat softening point: 95-105.degree. C.
Example 1
[0062] <Preparation of a composition>
[0063] PLA, PCL and Tackifier-1 were weighed in a mixing ratio
48.5:48.5:3.0, the percentage being by weight, and the mixture was
melt kneaded at 180.degree. C., using a uniaxial extruder of 40
mm.phi. to prepare COMPOSITION-1.
[0064] <Preparation of a film>
[0065] Using a uniaxial extruder provided with a T-die of 40
mm.phi. at the tip thereof, the COMPOSITION-1 was extruded at a
molding temperature of 180.degree. C. to obtain a non-stretched
film of 25 .mu.m in thickness.
[0066] <Manufacture of laminate film>
[0067] Using adhesive agents of polyurethane type (manufactured by
Takeda Pharmaceutical Ind. (Japan), a trade name TAKELAC A-968 and
TATELAC A-8) each in a ratio of 20% plus ethyl acetate in a ratio
of 60%, the aforementioned non-stretched film was dry laminated on
a biaxially stretched film of 25 .mu.m in thickness comprised of
PLA and stretched at a stretch ratio of 3.0.times.3.0 whereby a
laminate film of 52-53 .mu.m in thickness was obtained.
[0068] <Measurement of heat sealing strength>
[0069] 1. Heat seal characteristics to the non-stretched film
surface:
[0070] The surface of the non-stretched film in the laminated film
thus formed were overlapped each other and fixed by thermal fusion
under the condition of a given temperature for one second and a
seal surface pressure of 1 kg/cm.sup.2, using TP-701-B HEATSEAL
TESTER manufactured by Tester Ind. (Japan). By the way, heating was
limited only to the upper side of a heat seal bar of the tester at
a given temperature while the lower side of the bar was not heated.
The laminate film thus thermally fused was tested by a TENSILON
Universal Tester RTC-1225 manufactured by Orientec Inc. (Japan)
whereby the sample fixed by thermal fusion having a width of 15 mm
was peeled off at a tensile velocity of 300 mm/min and a maximum
strength at the test was referred to as a heat sealing
strength.
[0071] 2. Heat seal characteristics to the non-stretched PLA film
surface:
[0072] The surface of the non-stretched film in the laminated film
thus formed was overlapped with the surface of a PLA non-stretched
film of 50 .mu.m in thickness and measured a heat sealing strength
thereof in accordance with the above method.
[0073] 3. Heat seal characteristics to paper:
[0074] The surface of the non-stretched film in the laminated film
thus formed was overlapped with the surface of a paper (Nihon
Papaer Mfg. Inc., Japan; 300 .mu.m in thickness and a unit weight
of 260 g/m.sup.2) for cup and measured a heat sealing strength
thereof in accordance with the above method.
[0075] <Measurement of Young's modulus>
[0076] A sample of 15 mm in width and 100 mm in length in test
portion was cut out from the non-stretched film and measured for
Young's modulus at a tensile velocity of 5 mm/min., using a
TENSILON Universal Tester RTC-1225 marketed from Orientec Inc.
(Japan).
[0077] <Measurement of Haze>
[0078] Transparency (degree of haze) of the non-stretched film was
measured by using a Haze Meter 309A marketed from Nihon Denshoku
Kogyo KK (Japan).
Example 2
[0079] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-1 were
employed in a proportion of 47.5:47.5:5.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 3
[0080] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-2 were
employed in a proportion of 48.5:48.5:3.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 4
[0081] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-2 were
employed in a proportion of 47.5:47.5:5.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 5
[0082] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-3 were
employed in a proportion of 48.5:48.5:3.0 in terms of percentage by
weight in place of the composition used in Example 1.
Comparative Example 1
[0083] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA and PCL were employed in a
proportion of 50.0.50.0 in terms of percentage by weight in place
of the composition used in Example 1.
Example 6
[0084] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-1 were
employed in a proportion of 29.1:67.9:3.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 7
[0085] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-1 were
employed in a proportion of 28.5:66.5:3.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 8
[0086] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-2 were
employed in a proportion of 29.1:67.9:5.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 9
[0087] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-2 were
employed in a proportion of 27.0:63.0:10.0 in terms of percentage
by weight in place of the composition used in Example 1.
Example 10
[0088] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-3 were
employed in a proportion of 28.5:66.5:5.0 in terms of percentage by
weight in place of the composition used in Example 1.
Example 11
[0089] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and Tackifier-3 were
employed in a proportion of 29.1:67.9:3.0 in terms of percentage by
weight in place of the composition used in Example 1.
Comparative Example 2
[0090] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA and PCL were employed in a
proportion of 30.0:70.0 in terms of percentage by weight in place
of the composition used in Example 1.
Example 12
[0091] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL PBSA, and Tackifier-2
were employed in a proportion of 47.5:14.2:33.3:5.0 in terms of
percentage by weight in place of the composition used in Example
1.
Comparative Example 3
[0092] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA, PCL and PBSA were employed
in a proportion of 50.0:15.0:35.0 in terms of percentage by weight
in place of the composition used in Example 1.
Referential Example 1
[0093] A test was carried out in the same manner as described in
the foregoing Example 1 except that PLA alone was employed in place
of the composition used in Example 1.
Referential Example 2
[0094] A test was carried out in the same manner as described in
the foregoing Example 1 except that PCL alone was employed in place
of the composition used in Example 1.
Referential Example 3
[0095] A test was carried out in the same manner as described in
the foregoing Example 1 except that PCL and PBSA were employed in a
proportion of 30.0:70:0 in terms of percentage by weight in place
of the composition used in Example 1.
[0096] A result of the measurements obtained in Examples,
Comparative Examples and Referential Examples is shown in Tables 1
and 2 below.
1TABLE 1 A result of the measurements Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Com
Ex 1 Ex 6 Ex 7 PLA % by Weight 48.5 47.5 48.5 47.5 48.5 50 29.1
28.5 PCL % by Weight 48.5 47.5 48.5 47.5 48.5 50 67.9 66.5
Tackifler No. 1 1 2 2 3 -- 1 1 Tackifler % by weight 3.0 5.0 3.0
5.0 3.0 -- 3.0 5.0 haze (%) 6.8 6.5 7.8 8.4 9.8 7.7 14.1 15.0 MD
2070 2070 1980 1830 1980 2020 1020 1070 Young's modulus (MPa) 1860
1810 1820 1590 1730 1910 970 1010 TD Heat Sealing Strength Temp.
(.degree. C.) 65 3.9 0.3 70 0.8 1.0 0.5 1.2 1.9 0.7 19.5 9.9 80 4.1
5.3 4.3 6.4 8.2 6.0 19.1 15.5 Against 90 7.7 9.8 6.8 9.5 12.7 7.5
Non-stretched film 100 11.1 13.1 10.3 20.0 19.6 9.7 22.5 21.5 120
14.4 17.7 16.7 15.1 140 19.0 70 0.2 0.2 0.2 0.2 0.3 0.1 3.2 0.4 80
1.2 1.3 0.9 1.5 2.2 1.6 4.2 3.1 Against 90 6.8 7.1 6.7 7.0 7.8 4.6
7.8 7.1 PLA Non-stretched film 100 7.9 8.0 8.2 8.6 8.1 5.1 9.8 10.2
120 9.5 8.6 9.8 10.7 10.2 7.1 11.6 13.1 140 10.9 9.2 11.1 12.6 11.5
8.5 100 0.2 0.8 0.0 120 0.3 0.8 0.0 Against paper 140 0.8 1.2 0.1
160 1.7 1.8 0.7 Remarks: Ex: An abbreviation of Example Com: An
abbreviation of Comparative
[0097]
2TABLE 2 A result of the measurements (cont'd) Ex 8 Ex 9 Ex 10 Ex
11 Cm Ex 2 Ex 12 Cm Ex 3 Ref 1 Ref 2 Ref 3 PLA % by weight 28.1
27.0 28.5 29.1 30 47.5 50.0 100 -- -- PCL % by weight 67.9 63.0
66.5 67.9 70 14.2 15.0 -- 100 30 PBSA % by weight -- -- -- -- --
33.3 35.0 -- -- 70 Tackfler No. 2 2 3 3 -- 2 -- -- -- -- Tackifler
% by weight 3.0 10.0 5.0 3.0 -- 5.0 -- -- -- -- Haze (%) 14.8 27.3
22.6 19.4 13.6 3.4 4.0 2.5 13.6 13.0 Young's modulus MD 1400 1530
1230 1360 1460 1840 1840 3320 440 648 (MPa) TD 970 650 940 1300
1270 1720 1650 3120 640 750 Heat Sealing Strength Temp. (.degree.
C.) 65 0.4 0.3 0.5 0.2 0.2 0.2 70 4.8 17.1 1.5 1.3 5.5 0.0 0.0 0.2
0.2 0.0 80 19.9 i8.3 18.7 15.5 18.1 0.2 0.3 0.2 0.3 0.0 Against 90
0.7 0.5 0.5 0.3 0.0 NOn stretched 100 19.6 18.4 23.6 22.7 19.2 2.3
0.7 10.5 0.5 1.0 film 120 15.1 13.6 11.0 5.3 16.1 140 17.0 17.0
10.7 16.4 70 1.4 1.2 0.5 0.5 0.4 0.0 0.0 0.2 0.2 0.0 80 2.8 3.8 4.0
2.9 2.2 0.0 0.0 0.2 0.2 0.2 Against 90 5.5 7.5 9.2 9.2 3.4 0.2 0.2
0.2 0.3 0.6 PLA Non- 100 6.9 9.3 9.5 11.3 5.3 3.0 0.6 0.5 0.4 1.2
stretched film 120 8.3 11.6 13.6 13.8 7.0 6.3 4.6 10.5 6.2 5.2 140
9.6 11.6 8.5 12.7 6.3 11.0 6.4 8.2 100 0.4 0.8 0.3 0.3 Against
paper 120 0.7 1.7 0.3 0.3 140 0.9 2.5 0.5 0.5 160 1.6 3.0 0.5 0.5
Remarks: Ex: An abbreviation of Example Cm: An abbreviation of
Comparative Ref: An abbreviation of Referential Example
[0098] As is evident from the foregoing Examples and Comparative
Examples, the heat sealing strength of the laminate could be
enhanced without damaging transparency (haze) and flexibility
(Young's modulus) by adding Tackifier-1, -2 or -3, as in Examples
1-5, to a system of PLA/PCL=50/50 like Comparative Example 1. In
Examples 4 and 5, for Example, the heat sealing strength between
the surfaces at 100.degree. C. is about 2 times as much as the
value in Comparative Example 1, thus exhibiting outstanding effect.
It is also evident that the heat selling strength between the
non-stretched PLA film and paper is remarkably improved.
[0099] It was also confirmed that the heat sealing strength of the
laminate could be enhanced without damaging transparency (haze) and
flexibility (Young's modulus) by adding Tackifier-1, -2 or -3 as in
the case of Examples 6-10 to a system of PLA/PCL=30/70 like
Comparative Example 2. In Examples 6, 7, 9 and 10, for example, the
heat sealing strength against PLA non-stretched film at 100.degree.
C. is 1.5-2 times as much as the value of Comparative Example 2,
thus exhibiting outstanding effect. Moreover, the heat sealing
strength between the surfaces is improved. In comparison of Example
8 with Comparative Example 2, it is evident that a high degree of
improvement is achieved in the heat sealing strength against
paper.
[0100] It is understood that the preceding representative examples
may be varied within the scope of the present specification both as
to ingredients and treating conditions, by those skilled in the art
to achieve essential the same results.
[0101] As many widely different embodiments of the present
invention may be made without departing from the spirit and scope
thereof, it is to be construed that the present invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *